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The most complex subsystem in this project, at least in terms of the numbers of wheels (nearly 100), is the six-planet orrery which crowns the entire movement. In addition to the planets orbiting the sun, the two outer planets of Jupiter and Saturn have their own moons of four and five each respectively orbiting their parent planet. This adds a level of difficulty rarely seen in a mechanical orrery. The ring dials just below the orrery are the setting dials. Over all diameter of the orrery is just over 10". The model only has the planets out to Jupiter, but the actual orrery is designed to include Saturn. This orrery is based upon an astronomical clock made by Philipp Matthaus Hahn in 1780 as described in the German language book Astrnomische Uhren und Welt-Modelle der Priestermechaniker im 18. Jahrhundert vol. II Katalog, Ludwig Oechslin. I was very lucky to have found this two volume set. Here are photographed and described astronomical clocks, many with orrerys. Most importantly, however, is the fact that the author was allowed to disassemble and make schematics of these clocks. Along with the two volume set of books is a large folio containing these key schematics. It is this information that allowed me to even attempt such project. It also cut much research time off the subsystem making it affordable to add to the movement.

                   Astro orrery detail.JPG (868431 bytes)

Below are photos of Hahn's astronomical clock of 1780, as well as the orrery assembly out of the clock. Notice the tellurium on the left side of the clock. This clock having both the orrery and tellurium influenced my design choices. It is interesting to note that it also has a celestial sphere in the center. An item I had considered in my earlier designs before I ever saw this clock but was later abandoned in favor of a planisphere.

Astro orrery detail (1).jpg (513387 bytes) Astro orrery detail (2).jpg (522090 bytes)

Shown here is Hahn's original drawing for the orrery section of the clock. Next is the contemporary schematic including all wheel / pinion tooth counts.

Astro orrery detail (3).jpg (612558 bytes)   Astro orrery detail (4).jpg (187346 bytes)

The pictures below show to scale the relative distances the planets orbit from the sun as well as the planets relative sizes to each other. It becomes obvious, that to make the orrery fit into a reasonable space, some compromises have to be made in bringing in the two outer orbits toward the sun and to expand a bit away from the sun the three inner planets. The planets will still reflect their ranking in sizes to each other, but not to scale. And obviously the Sun is not to scale as it would be a s big as the entire orrery if built to scale!

                   Astro orrery detail (6).bmp (153478 bytes)  Astro orrery detail (7).bmp (172678 bytes)

Astro orrery detail (9).jpg (34353 bytes)   Astro orrery detail (8).jpg (32941 bytes)

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